"The binding site for MDMA and serotonin in the ion transporter is 100 percent conserved between octopus and human," researcher Eric Edsinger said.

The California two-spot octopus, Octopus bimaculoides, is mostly asocial, but when given MDMA, test specimens were more tolerant of other octopi. Photo by Tom Kleindinst/Marine Biological Laboratory

Sept. 20 (UPI) -- New research suggests octopi and humans use the same genetic coding to regulate serotonin uptake. The discovery, detailed this week in the journal Current Biology, highlights the evolutionary importance of serotonin regulation.

"If a gene sequence is conserved for 500 million years, it must be very important," Eric Edsinger, research scientist at the Marine Biological Laboratory, said in a news release.

Edsinger and his colleagues first noticed humans and octopi shared similar serotonin regulation genes in 2015, shortly after completing the first sequence of the octopus genome. Closer examination revealed the species used the same genes to regulate serotonin uptake.

The gene sequence found in genomes of both humans and octopi regulates a transporter protein that sucks up serotonin from the brain synapse, making room for newly released serotonin to be received.

Scientists believe the serotonin uptake process plays an important role in the way the drug MDMA binds with brain cells and affects a user's mood.

"The binding site for MDMA and serotonin in the ion transporter is 100 percent conserved between octopus and human," Edsinger said. "That is an extraordinary level of conservation. That means, pharmacologically, we could predict MDMA should work in octopus in the way it does in humans. It looks like it did."

For the new study, Edsinger and his research partners gave several California two-spot octopus specimens MDMA and observed their behavior.

California two-spot octopi, Octopus bimaculoides, are mostly asocial. They prefer to be alone. Scientists hypothesized the drugged octopi would be more tolerant of company, and tests showed they were.

"Octopuses aren't 100 percent asocial; they have some tolerance for each other," Edsinger said. "The drug probably amplified a low level of tolerance a bit."

Because the human brain and body -- as well as the genetic underpinnings -- are extraordinarily complex, comparing the genomes of humans and other animals can help scientists better understand which genetic and biological mechanisms are so important.